(Incorporates earlier USA-IRAN/SENATORS)
By Jeff Mason and Kevin Drawbaugh
WASHINGTON, June 21 (Reuters) - U.S. President Barack Obama expressed concern about violence and "unjust actions" against Iranian demonstrators on Sunday in a meeting with advisers who updated him on fast-moving events in the Islamic Republic.
"At approximately noon today, the President met for more than 30 minutes in the Oval Office with foreign policy advisors to get an update on the current situation and developments in Iran," a White House aide said in an email.
"At the meeting, the president reiterated his concerns about violence and unjust actions being taken against the Iranian people."
Obama's comments echoed a longer statement he released on Saturday urging the Iranian government to cease violent actions against its own people. Unrest has convulsed Iran for days since a disputed June 12 election that returned hardline anti-Western President Mahmoud Ahmadinejad to power.
Obama, a Democrat, has sharpened his tone amid the escalating violence and criticism from some Republicans, who accused him of timidity in his response.
"He's been timid and passive more than I would like," said Republican Senator Lindsey Graham on ABC's "This Week with George Stephanopoulos" television news program.
"We could be more forceful than we have," Republican Senator Charles Grassley said on CNN's "State of the Union" show.
Gunfire rang out in Tehran on Sunday after demonstrations culminated in the death of at least 10 people on Saturday. Iranian authorities dismissed the protesters as "terrorists" and rioters.
Senior Democratic senators defended the administration's approach, arguing that the president must walk a fine line.
Senator Robert Casey said Obama has achieved "the right balance. ... He's given a very tough, consistent line to the regime."
Casey said. "The president doesn't have the luxury of just thinking about the next couple of days. He's got to be able to think about the short-term, the long-term."
Pro-reform Iranian clerics stepped up criticism of the government in Tehran on Sunday after more than a week of defiance against Iran's leadership. Ahmadinejad won last week's election, according to official results. But his main challenger, Mirhossein Mousavi, has accused the government of electoral fraud and called on Iranians to protest.
Democratic Senator Christopher Dodd said U.S. support of the opposition could do it more harm than good.
"The question is, should the United States take ownership of this revolution?" Dodd said on ABC's "This Week." "I think we do great damage to the effort if it appears this is a U.S.-led effort.
Democratic Senator Dianne Feinstein also warned that too much outward U.S. support for dissenters could undermine them.
"It is very crucial ... that we not have our fingerprints on this, that this be truly inspired by the Iranian people," said Feinstein, who chairs the Senate Intelligence Committee, on CNN. She added that she did not know of any U.S. meddling in the Iranian election or in its aftermath.
On Saturday, Obama urged Tehran to "stop all violent and unjust actions against its own people."
Republican Senator John McCain, who lost the 2008 election to Obama, said on CBS' "Face the Nation," "I would like to see the president be stronger, although I appreciate the comments he made yesterday."
Obama, in the forefront of diplomatic efforts to halt an Iranian nuclear program the West fears could produce atomic weapons, recently acknowledged that the United States helped overthrow Iran's elected government in a 1953 coup that installed a pro-U.S. monarchy in power. That government was toppled by the 1979 Islamic Revolution.
Ahmadinejad warned the United States and Britain on Saturday not to interfere in Iran's affairs, according to Iran's official ISNA news agency. (Reporting by Jeff Mason, Kevin Drawbaugh and Alister Bull)